Regulatory Effects of AT1R-TRAF6-MAPKs Signaling on Proliferation of Intermittent Hypoxia-induced Human Umbilical Vein Endothelial Cells

摘要

Endothelial dysfunction induced by intermittent hypoxia(IH) participates in obstructive sleep apnea syndrome(OSAS)-associated cardiovascular disorders. Myeloid differentiation primary response 88(My D88) and tumor necrosis factor receptor-associated factor 6(TRAF6) regulate numerous downstream adaptors like mitogen-activated protein kinases(MAPKs) and the subsequent oxidative stress and inflammatory responses. This study aimed to characterize the role of My D88/TRAF6 in IH-treated cell function and its associated signaling. Human umbilical vein endothelial cells(HUVECs) were randomly exposed to IH or normoxia for 0, 2, 4 and 6 h. Western blotting was used to detect the expression pattern of target gene proteins [angiotensin 1 receptor(AT1R), p-ERK1/2, p-p38 MAPK, My D88 and TRAF6], and the relationships among these target genes down-regulated by the corresponding inhibitors were studied. Finally, the influence of these target genes on proliferation of HUVECs was also assessed by Ed U analysis. Protein levels of AT1R, TRAF6 and p-ERK1/2 were increased after IH exposure, with a slight rise in My D88 and a dynamic change in p-p38 MAPK. The down-regulation of TRAF6 by si RNA reduced ERK1/2 phosphorylation during IH without any effects on AT1R. Blockade of AT1R with valsartan decreased TRAF6 and p-ERK1/2 protein expression after IH exposure. ERK1/2 inhibition with PD98059 suppressed only AT1R expression. IH promoted HUVECs proliferation, which was significantly suppressed by the inhibition of TRAF6, AT1R and ERK1/2. The findings demonstrate that TRAF6 regulates the proliferation of HUVECs exposed to short-term IH by modulating cell signaling involving ERK1/2 downstream of AT1R. Targeting the AT1R-TRAF6-p-ERK1/2 signaling pathway might be helpful in restoring endothelial function.